Methods for producing cycloalkanol and/or cycloalkanone by cycloalkane oxidation with oxygen in the presence of mesoporous silica containing gold and/or cobalt has been known (Yingyong Huagong, Applied Chemical Industry, China, 2006, Vol. 35, p. 161-163, Gongye Cuihua, INDUSTRIAL CATALYSIS, China, 2006, Vol. 14, p. 56-60, and Korean Journal of Chemical Engineering, Korea, 1998, Vol. 15, p. 510-515).
The above described conventional methods, however, were not necessarily sufficient for their conversion rate of cycloalkane or selectivity to cycloalkanol and/or cycloalkanone.
According to the present invention, cycloalkanol and/or cycloalkanone can be produced with good conversion or selectivity.
The present invention relates to
a method for producing cycloalkanol and/or cycloalkanone,
which comprises reacting cycloalkane with molecular oxygen in the presence of mesoporous silica,
(1) the mesoporous silica containing at least one transition metal;
(2) the mesoporous silica having such pore distribution that the ratio of a total pore volume of mesoporous silica particles having a pore size of 3 to 50 nm to a total pore volume of mesoporous silica particles having a pore size of 2 to 50 nm is 50% or more; and
(3) the mesoporous silica being modified by an organic silicon compound (hereinafter referred to as “the present method”).
The present invention will be described in detail below.
The cycloalkane in this specification means saturated cyclic hydrocarbon with or without side chain(s).
The cycloalkane include, monocyclic cycloalkanes without a side chain on their rings, such as cyclopropane, cyclobutane, cyclopentane, cyclohexane, cycloheptane, cyclooctane, cyclodecane, and cyclooctadecane, and polycyclic cycloalkanes, such as decalin and adamantane, and cycloalkanes with side chain(s) on their rings, such as methylcyclopentane and methylcyclohexane. Two or more of the cycloalkanes may be used together in the present method.
An oxygen-containing gas is generally used as the source of molecular oxygen. This oxygen-containing gas may be, for example, air, pure oxygen, or those diluted with an inert gas such as nitrogen, argon or helium. Oxygen-enriched air obtained by adding pure oxygen to air can also be used.
Examples of the transition metal include, for example, vanadium, chromium, manganese, iron, cobalt, ruthenium, and palladium. In particular, cobalt is preferable. Two or more transition metals may be used together, if necessary. The content of the transition metal in the mesoporous silica is generally 0.01 to 20 wt %, preferably 0.05 to 10 wt %, and more preferably 0.1 to 5 wt %. The metal may be incorporated into a silica framework constituting the mesoporous structure, or it may be incorporated into the pores of the mesoporous silica, or it may be supported on the silica framework surface.
The mesoporous silica having a pore distribution with the ratio of a total pore volume of mesoporous silica particles having a pore size of 3 to 50 nm to a total pore volume of mesoporous silica particles having a pore size of 2 to 50 nm being 50% or more is usually used in the present method, and the ratio is preferably 70% or more, and more preferably 85% or more.
The pore distribution of the mesoporous silica can be known by measuring a pore size and a pore volume according to the Barrett-Joyner-Halenda (BJH) analysis of an adsorption isotherm by a volumetric method at a liquid nitrogen temperature (77 K). Then, the ratio of a total pore volume of mesoporous silica particles having a pore size of 3 to 50 nm to a total pore volume of mesoporous silica particles having a pore size of 2 to 50 nm can be calculated from pore distribution found by the measurements.
The specific surface area of the mesoporous silica used in the present invention is generally about 600 to 1500 m2/g.
The mesoporous silica used in the present method is a mesoporous silica containing at least one transition metal and having the specific pore distribution as described above and is modified by an organic silicon compound. Modification with the organic silicon compound is typically conducted by contacting a silicon compound capable of bonding to the surface of the mesoporous silica when contacted. Typical examples of the organic silicon compound include a silicon compound of formula (I):Si(R1)x(R2)4-x  (I)wherein R1 represents an alkoxy group, a hydroxyl group, a halogen atom, or a trialkylsilylamino group, R2 represents an alkoxy group, an alkyl group, an allyl group, an aryl group, or an aralkyl group, and x represents an integer of 1 to 3.
As the organic silicon compound particularly preferred is, trialkoxyalkylsilane or tetraalkoxysilane. The contact treatment is typically conducted by a method of immersing the crystal (silica having a mesoporous structure) after calcination in a liquid containing an organic silicon compound, or by a method of bringing a crystal (silica having a mesoporous structure) after calcination into contact with a gas containing the organic silicon compound.
The amount of the organic silicon compound that may be used is generally 1 to 10000 parts by weight, preferably 5 to 2000 parts by weight, and more preferably 10 to 1500 parts by weight per 100 parts by weight of the silica before the contact treatment with the organic silicon compound.
A temperature for the contact treatment with an organic silicon compound is generally 0 to 300° C., and preferably 30 to 250° C. A time for the contact treatment is generally 0.1 to 50 hours, and preferably 1 to 20 hours.
The mesoporous silica containing at least one transition metal and having the specific pore distribution is typically prepared by
1) performing a hydrothermal synthesis reaction with a mixture containing tetraalkoxysilane, a predetermined structure-directing agent, and water (said mixture is referred to as “mixture for hydrothermal reaction”) to obtain a crystal (silica having a mesoporous structure),
2) calcining the crystal to obtain mesoporous silica, and
3) contacting the calcined crystal with at least one transition metal compound.
Alternatively, the mesoporous silica containing at least one transition metal and having the specific pore distribution is prepared as follows. For example, the transition metal compound, such as halide, nitrate, carboxylate, and oxoate (oxyacid salt) of the transition metals, is mixed with tetraalkoxysilane, a predetermined structure-directing agent and water, and the resulting mixture is subjected to a hydrothermal synthesis reaction to obtain a mesoporous silica crystal containing the transition metal compound.
The predetermined structure-directing agent is suitably selected. For preparing SAB-3 type mesoporous silica a gemini surfactant (e.g., CnH2n+1(CH3)2N+(CH2)SN+(CH3)2CmH2m+1, wherein n s, and m each represent an integer of 1 or more) is selected as a structure-directing agent as described in Catalysis Communications, Holland, 2008, Vol. 9, No. 13, p. 2287-2290.
For HMS type mesoporous silica, long chain alkylamine (CnH2n+1NH2, wherein n represents a integer of 1 or more) is selected as a structure-directing agent as described in Applied Catalysis A: General, Holland, 2008, Vol. 347, p. 133-141.
For MSU-X type mesoporous silica, oleyl decaoxyethylene is selected as a structure-directing agent as described in Microporous and Mesoporous Materials, Holland, 2008, Vol. 109, p. 199-209.
For SBA-12 type mesoporous silica, polyethylene oxide is selected as a structure-directing agent as described in Journal of Physical Chemistry B, USA, 2002, Vol. 106, p. 3118-3123.
For SBA-15 type mesoporous silica, a triblock copolymer (polyethylene oxide-polypropylene oxide-polyethylene oxide copolymer) is selected as a structure-directing agent as described in Science, USA, Vol. 279, p. 548-552, and Microporous and Mesoporous Materials, Holland, 2006, Vol. 91, p. 156.
For preparing SBA-16 type mesoporous silica, a triblock copolymer (polyethylene oxide-polypropylene oxide-polyethylene oxide copolymer) is selected as a structure-directing agent as described in Microporous and Mesoporous Materials, Holland, 2007, Vol. 105, p. 15-23.
Among these, SBA-12 type, SBA-15 type, and SBA-16 type mesoporous silica are preferable, and SBA-15 type is more preferable. Among the above structure-directing agents, in particular, polyalkylene oxide such as polyethylene oxide and a triblock copolymer (polyethylene oxide-polypropylene oxide-polyethylene oxide copolymer) are preferable. A molecular weight of the polyalkylene oxide referred herein is usually about 500 to 15000. The triblock copolymer usually used herein has a polymerization unit ratio by weight of polyethylene oxide:polypropylene oxide:polyethylene oxide about 5:70:5 to 110:70:110.
The structure-directing agent is generally used in an amount of 0.1 to 1 mol, and preferably 0.2 to 0.5 mol per mol of the tetraalkoxysilane. The amount of water is generally 5 to 30 parts by weight, and preferably 10 to 15 parts by weight per part by weight of the tetraalkoxysilane. In addition, acids, for example, inorganic acids such as hydrochloric acid (aqueous solution of hydrogen chloride) and sulfuric acid, and organic acids such as acetic acid and citric acid, and bases such as sodium hydroxide and potassium hydroxide may be added to the mixture, if necessary, to perform a hydrothermal synthesis reaction.
The reaction temperature of the hydrothermal reaction is generally 20 to 200° C., and preferably 20 to 150° C. The reaction time is generally 0.1 to 400 hours, and preferably 1 to 200 hours.
The contact of the calcined crystal (mesoporous silica) with at least one transition metal compound is conducted by impregnation, in which the crystal (mesoporous silica) is immersed in the solution of the transition metal compound to adsorbed the transition metal, or the crystal is subjected to ionic exchange with a cation of the crystal.
Calcination temperature is generally about 500 to 600° C., and calcination time is generally 1 to 20 hours.
The mesoporous silica thus obtained is then treated by contacting with the organic silicon compound. Desired mesoporous silica can be thus obtained. Then, cycloalkane is oxidized with molecular oxygen in the presence of this mesoporous silica. The mesoporous silica is generally used in an amount of 0.01 to 50 parts by weight, and preferably 0.1 to 10 parts by weight per 100 parts by weight of the cycloalkane.
A reaction temperature for oxidizing cycloalkane is generally 0 to 200° C., and preferably 50 to 170° C., and a reaction pressure is generally 0.01 to 10 MPa, and preferably 0.1 to 2 MPa. A reaction solvent can be used, if necessary, and for example, nitrile solvents such as acetonitrile and benzonitrile, carboxylic acid solvents such as acetic acid and propionic acid, and the like can be used.
Post-treatment operations after the oxidation reaction are not limited, and examples thereof include such as a method in which a reaction mixture is filtered to separate a catalyst, then washed with water, and subsequently distilled to obtain a reaction mixture.
Cycloalkyl hydroperoxide resulting from cycloalkane that may be contained in the reaction mixture can be converted into desired cycloalkanol or cycloalkanone, for example, by an alkali treatment, reduction treatment or the like.